The Nature of Free Will

[Trigshot]

I have a subject I wish to discuss, which has been interesting me for some time now. The issue of free will. Does it exist?

First, there's the common explanation of determinism, the idea that if every particle in all of the universe could be measured to have a position and velocity, then the next moment could be predicted. However, this breaks the Heisenberg Uncertainty Principle, which says that the velocity and position of a particle cannot be measured at the same time.

Suppose that instead of an instant, you had two consecutive snapshots over a given interval, in which the difference between the particles could be measured to determine velocity. Would that then provide a scenario for determinism?

Does the concept of measuring position and velocity at the same time break the laws of physics, or do we simply not have the correct set of tools in which to measure such subtle measurements?

I am inclined to side with the Uncertainty Principle, but like Einstein, I find myself conflicted and at disbelief with the reality of uncertainty. It is simply difficult to grasp, that because of an infinite number of possibilities at any given moment, anything and everything has happened, will happen, and is happening at this very moment in alternate realities.

Its okay to feel confused if you don't understand what I just said. I'm not sure I do either.

 

[Mapp]

I suppose it is remotely possible that there is no such thing as free will. And that every decision, even the most spur of the moment, irrational and impulsive decision can be tracked to environmental, and past history. But you're dealing with such a nearly infinite multitude of variables, that I imagine it would be immeasurable. Every time someone tries to plot a model for human behavior, humans invariably break the model. So perhaps free will should just be assumed.

 

[Ozymandyus]

I have a subject I wish to discuss, which has been interesting me for some time now. The issue of free will. Does it exist?

Does the concept of measuring position and velocity at the same time break the laws of physics, or do we simply not have the correct set of tools in which to measure such subtle measurements?

I've always seen the uncertainty principle as a commentary on our inability to directly observe subatomic particles. To obtain measure of position, we must observe an interaction between the particle and the thing which we use to measure - we cannot perceive the particle directly with no physical interaction with the particle. That interaction changes the particles velocity. What ways of measuring do we have that do not interact in any way? Ah well, I realize that I don't fully understand it...

Anyway if we were somehow able to take two state measurements of the universe, I do believe that the universe would be only partially deterministic still, as certain particles behave within probabilities even discounting the uncertainty principle, for example, particular decaying atomic particles. These probabilistic events will effect the deterministic ones so that we could not actively calculate future states.

As for a physical existence of all possible realities in alternate universes... perhaps. I see no need to posit such alternate universes, it seems more a thought exercise in what could be rather than a commentary on reality. That thoughts seem to be non-deterministic and we imagine things that don't seem to follow from physical laws is an interesting possible source of free will, or its illusion.

Beyond that: An awesome extensive discussion of this issue by Daniel Dennett is contained in 'Freedom Evolves'. He makes an argument a certain type of free will even in a completely deterministic universe.

 

[Pulsar]

Suppose that instead of an instant, you had two consecutive snapshots over a given interval, in which the difference between the particles could be measured to determine velocity. Would that then provide a scenario for determinism?

No, all you did was determining what the path of a particle was in the past. You wouldn't be able to predict its future path. Basically you did something like a single-slit experiment: a particle passes a slit and hits a screen. If you repeat this many times, the positions on the screen will be distributed like a gaussian, reflecting the different momenta of the particles. There's no way of predicting beforehand where a particle will hit the screen.

Does the concept of measuring position and velocity at the same time break the laws of physics, or do we simply not have the correct set of tools in which to measure such subtle measurements?

It really breaks the laws of physics, our measurements make no difference. The Uncertainty Principle is often confused with the Observer Effect, i.e. that the observation itself influences the particle. Such influences can be avoided, and even then the Uncertainty Principle holds.

Btw, there are already several threads on determinism and free will. Check here and here on the old forum, and here and here on this forum.

 

[Trigshot]

To obtain measure of position, we must observe an interaction between the particle and the thing which we use to measure - we cannot perceive the particle directly with no physical interaction with the particle.

At the current moment, yes this is true. However, just because we cannot measure the particle without physical interaction does not mean that the particle's position and velocity are immeasurable. It simply means that our instrumentation is inadequate for measuring such particles. The accuracy of measurement should have no effect on the ability to be measured.

I do understand, however that there is a paradox forming. There is a point at which it may be impossible to create a device for measuring such amazingly small particles, because the device will have to at least be made of particles the same size.

One more thing that contradicts determinism is the potential for acceleration of particles. IF one could know position and velocity at the same time, the next moment COULD be predicted, but if a particle decelerates or accelerates, the variable velocity may account for a variation in moments in time.

Btw, there are already several threads on determinism and free will. Check here and here on the old forum, and here and here on this forum.

Sorry I realized there probably were some other topics, this is just may laziness kicking in, not taking the time to go dig for old threads.

 

[Sparky]

I do understand, however that there is a paradox forming. There is a point at which it may be impossible to create a device for measuring such amazingly small particles, because the device will have to at least be made of particles the same size.

Yes. This is at a value of h/(4pi) (if memory serves me correctly).

Free will - Our actions are/behaviour is the result of chemical reactions that we cannot control. Surely this means that free will is an illusion of the mind? (I don't want to believe this but no one has really been able to tell me what is wrong with it)

Determinism - As we cannot measure the exact position and velocity of a given particle, we will only be able to predict the most probable outcome of a given situation and never the exact one so there is semi-determinism but the universe is not fully deterministic.

 

[GoodKat]

Determinism - As we cannot measure the exact position and velocity of a given particle, we will only be able to predict the most probable outcome of a given situation and never the exact one so there is semi-determinism but the universe is not fully deterministic.

We do not have to be able to predict it for it to be deterministic, it just simply has to always follow the same rules.

 

[Pulsar]

However, just because we cannot measure the particle without physical interaction does not mean that the particle's position and velocity are immeasurable. It simply means that our instrumentation is inadequate for measuring such particles.

No, to quote wiki:

The uncertainty principle is often explained as the statement that the measurement of position necessarily disturbs a particle's momentum, and vice versa,i.e., that the uncertainty principle is a manifestation of the observer effect.

This common explanation is incorrect, because the uncertainty principle is not caused by observer-effect measurement disturbance. For example, sometimes the measurement can be performed far away in ways which cannot possibly "disturb" the particle in any classical sense. But the distant measurement (of momentum for instance) still causes the waveform to collapse and make determination of (position for instance) impossible. This queer mechanism of quantum mechanics is the basis of quantum cryptography, where the measurement of a value on one of two entangled particles at one location forces, via the uncertainty principle, a property of a distant particle to become indeterminate and hence unmeasurable. If two photons are emitted in opposite directions from the decay of positronium, the momenta of the two photons are opposite. By measuring the momentum of one particle, the momentum of the other is determined, making its position indeterminate.

This disturbance explanation is also incorrect because it makes it seem that the disturbances are somehow conceptually avoidable , that there are states of the particle with definite position and momentum, but the experimental devices we have could never be good enough to produce those states. In fact, states with both definite position and momentum just do not exist in quantum mechanics, so it is not the measurement equipment that is at fault.

It is also misleading in another way, because sometimes it is a failure to measure the particle that produces the disturbance. For example, if a perfect photographic film contains a small hole, and an incident photon is not observed, then its momentum becomes uncertain by a large amount. By not observing the photon, we discover indirectly that it went through the hole, revealing the photon's position.

 

[Trigshot]

Thank you Pulsar/Wikipedia. That is exactly what I wanted to know. That makes much more sense to me.

 

[Pulsar]

I'm starting to feel like a wiki scientist
Glad to help.

 

[philebus]

I remember reading a comment by J L Austin, where he questions if anyone really has a clear idea of free will at all. I think he had a point - before asking if we can have free will, we need to be able to say just what it is. Austin did make one suggestion, that instead of free will, we might find it easier to talk about responsibility instead.

As an asside, I have to wonder....if my choices are not determined, then they must be uncaused? And if uncaused, in what way are they choices that I make as opposed to events that just happen to me?